Iowa is well known for producing high quality beef carcasses. Often, cattle are managed to optimize marbling development and carcass quality when marketing for carcass premiums, even if that means compensating feedlot performance and efficiency.
A recent ISU study was designed to evaluate practical ranges for conservative versus aggressive feeding strategies and implant strategies to determine the optimum level for managing efficiency and carcass quality on today’s cattle.
Fifty-four Angus steers (n = 9/treatment) from the ISU McNay Research Farm cow herd were fed for 144 days at the ISU Armstrong Research Farm in pens equipped with bunks capable of monitoring individual animal intake. Steers were allotted between two nutritional programs: 1) a lower energy finishing ration (59 NEg, 18% roughage level; LE) or 2) a higher energy finishing ration (63 NEg, 8% roughage; HE). Within each dietary treatment, one of three implant strategies was applied: 1) no implant (NIMP); 2) a conservative implant strategy (total of 160 mg trenbolone acetate (TBA) delivered throughout the study; Revalor-IS on d0 and d74; RIS); or 3) an aggressive implant strategy (total of 400 mg TBA delivered throughout the study; Revalor-200 on d0 and d74; R200). All steers were harvested on the same day at Iowa Premium.
As expected, steers fed the LE diet had lower ADG and final weights compared to steers on the HE diet (Table 1). Intake was not affected by diet, but the differences in growth resulted in higher feed conversions when fed LE compared to the HE.
For implant strategies, ADG and final weights linearly increased as TBA dosage increased. While intake was consistent across treatments, feed conversion was positively impacted by implants and resulted in a 33% decrease in feed required to add an additional pound of gain between steers who received a R200 implant compared to steers receiving no implant.
Overall, steers on this study graded 100% Choice and higher, 55% Prime, and 15% yield grades 4 and 5. Of most interest, implant strategy had no impact on marbling score (Figure 1). However, steers fed the LE diet tended to have lower marbling scores, which is likely attributed to lower growth performance and less finish on steers.
In summary, the use of implants demonstrated no adverse side effects on marbling or carcass quality and improved growth performance and feed efficiency. When fed the same amount of days on feed, the use of a lower energy diet hurt performance and carcass quality.
Results of this study show that when managed appropriately, the use of implants and nutrient-dense diets can effectively allow for optimizing efficiency without sacrificing quality.
This project was funded by the Iowa State Beef Checkoff Program.